Rotary bladed or like assembly



July 28, 1953 E. M. BUTCHER ROTARY BLADED OR THE LIKE ASSEMBLY FiledDec. 6, 1948 RH W ///////////A I lnvehgor 4 4: Attorneys Patented July28, 1953 ROTARY BLADED 0R LIKE ASSEIWBLY Edgar Malcolm Butcher, Blaby,England, assignor to Power Jets (Research and Development) Limited,London, England, a British company Application December 6, 1948, SerialNo. 63,788 In Great Britain December 13, 1947 4 Claims.

This invention relates to rotary bladed or like structures comprising aplurality of blades or vanes, each extending in a radial orsubstantially radial direction and lying wholly or partly in a plane orplanes other than a plane of rotation, one or more of said blades orvanes being divided in a plane of rotation into two sections havingtheir adjacent edges in axial abutment or in close proximity so as toform in effect a single blade or vane. A structure of this kind issometimes found to be a constructional convenience in that it simplifiesthe manufacture of a rotor having blades or vanes of complex form byenabling the complete rotor to be made in two parts, each carryingsections of blades or vanes, the two parts being subsequently assembledby bolting together with the respective blade or vane sections in axialalignment and either abutting or in close proximity. A case to which theinvention is particularly applicable is that of a centrifugal impellerin which the radial vanes have curved entry edges and in which, in orderto simplify manufacture, the rotor is made in two parts separated in aplane of rotation, one of which parts carries the curved entry edgesection and the other the main section of each vane, the two rotor partsbeing secured together so that the curved entry vane sections are inclose proximity to or abut against and are in axial alignment with themain vane sections.

On the other hand the construction of a bladed or vaned rotor in twoparts in this manner gives rise during operation to difiiculties inmaintaining alignment of the axially abutting edges, particularly inthat trouble may be encountered due to aerodynamically or mechanicallyexcited vibration of the individual section relative to one another.These difficulties render necessary very accurate manufacture andfitting in order to ensure suitable contact pressure between the twosections of each blade, and uniformity of such pressure from blade toblade, and it is an object of the present invention to provide aconstruction which will reduce the necessity for such high accuracy.

For the purpose according to the invention a rotary bladed or likestructure of the kind specified is provided, between the axially alignededges of the two sections of a blade, with an interconnecting elementadapted to resist relative displacement between the blade sections in aplane of rotation containing said element, the latter being movablealong guide means over a path corresponding to the required line ofalignment between the two blade sections and exerting during saidmovement a wedging action with respect to said guide means, provisionbeing made for the element to move so as to take up any slack in theconnection whilst tending by said wedging action to maintain the bladesections in their proper axial alignment.

Preferably the movement of the element is derived primarily fromcentrifugal loading of said element occurring when the structure isrotating, but it may also be derived to a major or minor degree fromspring means provided for the purpose.

In one form of the invention each of a pair of axially abutting bladesections has a groove in its abutting edge, the two grooves togetherforming for an interconnecting element in the form of a plug which seatsin and between the grooves, a guide path following the line of abutmentand tapering in the radially outward direction, the plug beingdimensioned to be a slightly slack fit in the grooves when at itsradially inner position, so that under centrifugal loading it can moveradially outwards until it reaches a position at which it wedges in thegrooves. When this position is reached the two blade sections will beeffectively interconnected so as to restrain relative movement thereofin the corresponding plane of rotation.

The rigidity of such connection is to some extent controllable by theshape of the grooves and material of the plug, and it is thus possibleto have a substantially rigid interconnection, or to provide aninterconnection whcih will deliberately permit a small relative movementbetween the blade sections whilst providing forces which will tend toreduce vibration.

The centrifugal loading of the plug may be augmented by the addition ofa weighting part of the same or heavier material which need not par-,ticipate in the wedging action, or by the use ofsprings. In the latterevent means may be provided to ensure that the spring load is notapplied to the plug until the two blade sections have been assembledtogether.

- In its application to the rotor of a centrifugal impeller having moreor less radial vanes made in two sections comprising a curved intakesection and a relatively plane main section carried by separate rotorbodies which are secured together coaxially with the edges of the twosets of vane sections in axial alignment, the said edges of each sethave guide channels formed therein and are interconnected by plugsoperating in the guide channels in the manner above described.

By way of example various forms of the invention are hereinunderdescribed with reference to the accompanying drawings in which:

Figure 1 is an axial section of part of a centrifugal impeller showingone form of the invention;

Figure 2 is a section on the line II--II of Figure 1,

Figure 3 is a section on the line III-III of Figure 1;

Figure 4 is an enlarged detail of Figure 1;

Figures 5 and 6 are detail views showing modified forms of theinvention.

In Figure 1 a double sidedcentrifugalimpelleir comprises a hub la, lb,having a number of ra dially extending vanes each made up-of twosections 2a, 2b, the impeller being mounted: tor rotation on a hollowshaft 3. The whole-impeller structure is divided into two parts in aplane of rotation containing the line II-II, the main part of theimpeller containing the hub la and the vane sections 2a'whilethesmallerpart of the 1H1.- peller contains the hub portion th and. the vane?sections 2b the radially inner edgesof which: are suitably bent orcurved over so as to form inlet: guide vanes;

The shaft 3 and the two parts In; 2a: and lab, 2b; of the impeller areheld: together by bolts 9 passing through a flange Baron shaft 3; theedges 4a,. 4b of the vane sections 2a, 2b respectively'being thus heldin close proximity or abutment along the line 14 and in axial alignmentwith one another.

In each of these edges. 4a, 4b is. formed a V- shaped groove orchannel?5a, 5b as showrrin Figure 3, the edges being shown slightly separated.for clarity. As seen in Figure 4 the radially outer' positions of thegrooves 5a, 5b; are gradually tapered within the space enclosed by thegrooves 5a, 5b and slidablewithinzthem is a plug 6 of citcular sectionand frusto-conicali form, and having a lower portion T heavier than theportion; 6 and of the same or different material. As the impellerrotates, the plug 6,. 1' is moved; radiallyoutwards by centrifugal forceand the part 6- becomes wedged between. the radially outer" ends of. thegrooves 511; 5b. With the plug: in this posi.-- tion', the two vanesections 21:, 2b become firmly interconnected so as to prevent relative;move-- ment between them in the plane of rotation: containing the plug.

The object of the heavier part. I: of theplug; isto augment thecentrifugal loading on the plug: 6', and the part I need not thereforeparticipate in the wedging action. The plug 6 may of course: itself beformed as a single element which. itself occupies the greater length. ofthe grooves;

The plug 6 may of. course: have a section other than circular, e. g.square; and maybe ofmetal, but if vibration damping is the effectprimarily required; the material of the plug may beone: having gooddamping properties, for example, vulc anise d fibre.

In Figure 5 the plug 6- isof circular section and is seated in grooves5a, 5b, having an arcuate cross-section of greater radius than that ofthe plug 6 soas to permit some degree of lateral movement of the plugand thus a limited lateral movement between the blade sections 2a, 2b inthe plane of rotation containing the plug.

In the construction of Figure 1 the centrifugal loading on the plug 6,7, is augmented by the addition of a heavier part1. Alternatively thecon:- trifugal loading may be augmented by the use of a spring, meansbeing provided to-ensure that the.

spring load is not applied to the plug until the blade sections areassembled. Such an arrangement is shown in Figure 6 in which the shaft 3on which the centrifugal impeller is mounted is provided with a cam facel0 and a pin II can bear against a spring I2 adapted to act on thepart 1. The pin Ill can extend radially inwardly into a shaft socket f3and when the shaft 3 is inserted into this socket the cam face It movesto the position shown in broken lines thus moving pin H radiallyoutwards to compress spring I2 and thereby to urge part radiallyoutwards.

By means. of the invention the need for a high degree of dimensionalaccuracy and individual adjustment ofthe aligned edges of the vanesections is thus avoided since each pair of vane sections isinterconnected independently of any other pair and the accuracy ofalignment of the sections. of a pair is automatically maintained by theplug taking up differing radial positions under' the influence of.centrifugal. force.

It. is. to: be. understood that. although the. in:- vention. has been.described as primarily applicable to a. centrifugal impeller, theprinciple; of construction involved is equally applicable to. an axialflow. type. of compressor or to. any other bladed structure in. whichrelatively thin rotor. blades. or vanes are. required to be in edge.contact, or in a condition closely approachin edge to. edge. contact, ina plane of rotation.

I claim 1.

1. A rotary bladed. impeller structure compris.-- ing a hub, a series ofblades. radiating fromsaid hub, individual blades. being divided along aplane of rotation. into at least twosections having their adjacent edgesclose proximity, each. of. said adjacent edges. having a grooveextending, there-along from the hub. to the neighborhood. of the blade;tip, toform in each blade. a radially extending" tapered cavity whichmeasured the plane of rotation of. theblade division is smallest nearthe tip and biggest near the hub, in. com.- bination Witha wedge-shapedplug lying. in said groove and proportioned to fit the said cavity whenmoved radially outwards under the. action. of centritugal force, so thataccordingly it wedges. in the grooves and keys the adjacent blade sections. together.

2. A. rotary bladed structure as setforth in claim 1, wherein saidgroove in each of the pair of adjacent edges is of arcuate crossesectionand the wedge-shaped plug is of circular cross-section.

3- A rotarybladed structure according to claim 1-,. wherein saidcavityisformed with an enlarged; spacev at its inner radial end and the Wedge--shaped plug has an enlarged head housed in. said enlarged space.

4-. A rotary bladed structure as set forth in claim 1 includingabutments radially movably mounted thereon. below the radially innerends of said wedge-shaped plugs, and springs. compressed between saidplugs and said abutments in: a position to urge said. plugs radiallyoutwardsl EDGAR MALCOLM BUTCHER- References. Cited in the file of thispatent UNITED STATES. PATENTS Number Name Date 2,147,005 Williams Feb.14, 1939 2,310,412. Flanders Feb. 9, 194-3 2,405,283 Birmann Aug. 6,1946 2,412,615 Howard Dec. 17, 1946

